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Biomedical subjects

M Lombardi

Publications and source records attributed to M Lombardi.

At least 55 records · Page 3Linked to original sources
PubMed1995

Ergonovine-echo test to assess the significance of chest pain at rest without ECG changes.

The aim of this study was to assess the feasibility and diagnostic role of ergonovine maleate infusion under continuous two-dimensional echocardiographic monitoring for the identification of vasospastic myocardial ischaemia in patients with chest pain at rest not associated with diagnostic ECG changes. One hundred and twenty-eight consecutive patients, selected on the basis of absence of ischaemic ECG changes during angina at rest before or during hospitalization, were enrolled in the study. Ergonovine maleate was i.v. administered in scaled doses (from 0.025 to 0.2 mg at 10 min intervals) under echocardiographic, electrocardiographic and systemic blood pressure monitoring. Wall motion asynergies were observed in 33 patients, accompanied by typical chest pain in 24 patients and by ECG changes in 25 (ST elevation in 13 patients, ST depression in seven, T wave changes in five). All patients were able to complete the test. Non life-threatening ventricular arrhythmias were observed in four patients exclusively in association with ischaemia. In seven patients with a positive test, coronary artery spasm was documented at angiography. In 16 patients with a positive test, the vasospastic event was reproduced by a hyperventilation-echo test or a second ergonovine maleate-echo test performed within 3 days of the first examination. In none of the patients with a negative test was documentation of myocardial ischaemia due to a primary reduction in coronary blood flow. Thus, in patients who do not show ECG changes during chest pain at rest, the ergonovine maleate-echo test is feasible and safe; it permits the recognition of ischaemic episodes on the basis of wall motion abnormalities when conventional 12-lead ECG-recorded chest pain is non-diagnostic.

Adult↗
PubMed1995

[Early gastric cancer].

The authors perform a retrospective analysis of 46 cases of EGC referred to the Surgical Division of Carrara Civic Hospital during the period 1980-1990 who subsequently underwent surgery. Data relating to age, symptomatology and endoscopic examinations were analysed in order to evaluate the real diagnostic penetration of the method in association with tumour biopsy, site, macroscopic aspect, possible lymph node involvement and the histology of lesions. The most frequent form of surgery in this series was subtotal gastrectomy and the 5- and 10-year survival rates, calculated using an actuarial method, were compared with data reported in the literature. The authors conclude by emphasising the need to improve the frequency of diagnosis of gastric cancer at an "early" stage and affirm that gastric resection associated with lymphoadenectomy of 1st and 2nd level lymph nodes is a sufficiently radical operation and less punitive for the patient compared to total gastrectomy given that the 5- and 10-year survival rates are comparable.

Adult↗
PubMed1994

Molecular cloning, primary structure, and characterization of two members of the mammalian electroneutral sodium-(potassium)-chloride cotransporter family expressed in kidney.

Electrically silent Na(+)-(K+)-Cl- transporter systems are present in a wide variety of cells and serve diverse physiological functions. In chloride secretory and absorbing epithelia, these cotransporters provide the chloride entry mechanism crucial for transcellular chloride transport. We have isolated cDNAs encoding the two major electroneutral sodium-chloride transporters present in the mammalian kidney, the bumetanide-sensitive Na(+)-K(+)-Cl- symporter and thiazide-sensitive Na(+)-Cl- cotransporter, and have characterized their functional activity in Xenopus laevis oocytes. Despite their differing sensitivities to bumetanide and thiazides and their different requirements for potassium, these approximately 115-kDa proteins share significant sequence similarity (approximately 60%) and exhibit a topology featuring 12 potential membrane-spanning helices flanked by long non-hydrophobic domains at the NH2 and COOH termini. Northern blot analysis and in situ hybridization indicate that these transporters are expressed predominantly in kidney with an intrarenal distribution consistent with their recognized functional localization. These proteins establish a new family of Na(+)-(K+)-Cl- cotransporters.

Amino Acid Sequence↗
PubMed1994

Monitoring of the discrimination threshold for interocclusal thicknesses in rehabilitated edentulous patients.

Thirty-seven white Caucasian subjects with unsatisfactory dentures were tested for interocclusal thickness discrimination threshold. New dentures were prepared and the test was repeated on days 1, 4 and 90 (from delivery). Eight patients whose situation was still unsatisfactory were given osseointegrated implant anchored dentures and the test repeated at the same intervals. Results were analysed statistically. Improved denture fit was found to increase interocclusal sensitivity. Decreased sensitivity during follow-up might indicate the need to check denture fit.

Aged↗
PubMed1994

[Corneal reinnervation after lamellar keratoplasty in comparison with epikeratophakia and photorefractive keratectomy].

Corneal sensitivity was examined with the Draeger aesthesiometer in 8 patients after lamellar keratoplasty, 7 patients after epikeratophakia and 82 patients after photorefractive keratectomy. We examined 9 different points in each cornea. The corneal sensitivity of patients after lamellar keratoplasty was normal 1 year after operation. A correlation with the depth of the lamellar dissection was demonstrated. Patients with lamellar keratoplasty with pterygium showed a sensitivity decrease in the nasal parts of the lenticule even after one year. Three years after epikeratophakia the corneal center was still not sensitive. After photorefractive keratectomy of more than 10 D, corneal hyposensitivity was shown even 2 years after operation.

Adult↗
PubMed1993

Cloning and characterization of an extracellular Ca(2+)-sensing receptor from bovine parathyroid.

Maintenance of a stable internal environment within complex organisms requires specialized cells that sense changes in the extracellular concentration of specific ions (such as Ca2+). Although the molecular nature of such ion sensors is unknown, parathyroid cells possess a cell surface Ca(2+)-sensing mechanism that also recognizes trivalent and polyvalent cations (such as neomycin) and couples by changes in phosphoinositide turnover and cytosolic Ca2+ to regulation of parathyroid hormone secretion. The latter restores normocalcaemia by acting on kidney and bone. We now report the cloning of complementary DNA encoding an extracellular Ca(2+)-sensing receptor from bovine parathyroid with pharmacological and functional properties nearly identical to those of the native receptor. The novel approximately 120K receptor shares limited similarity with the metabotropic glutamate receptors and features a large extracellular domain, containing clusters of acidic amino-acid residues possibly involved in calcium binding, coupled to a seven-membrane-spanning domain like those in the G-protein-coupled receptor superfamily.

Amino Acid Sequence↗
PubMed1993

Primary structure and functional expression of a cDNA encoding the thiazide-sensitive, electroneutral sodium-chloride cotransporter.

Electroneutral Na+:Cl- cotransport systems are involved in a number of important physiological processes including salt absorption and secretion by epithelia and cell volume regulation. One group of Na+:Cl- cotransporters is specifically inhibited by the benzothiadiazine (thiazide) class of diuretic agents and can be distinguished from Na+:K+:2Cl- cotransporters based on a lack of K+ requirement and insensitivity to sulfamoylbenzoic acid diruetics like bumetanide. We report here the isolation of a cDNA encoding a thiazide-sensitive, electroneutral sodium-chloride cotransporter from the winter flounder urinary bladder using an expression cloning strategy. The pharmacological and kinetic characteristics of the cloned cotransporter are consistent with the properties of native thiazide-sensitive sodium-chloride cotransporters in teleost urinary bladder and mammalian renal distal tubule epithelia. The nucleotide sequence predicts a protein of 1023 amino acids (112 kDa) with 12 putative membrane-spanning regions, which is not related to other previously cloned sodium or chloride transporters. Northern hybridization shows two different gene products: a 3.7-kb mRNA localized only to the urinary bladder and a 3.0-kb mRNA present in several non-bladder/kidney tissues.

Amino Acid Sequence↗
PubMed1993

Flow quantitation by radio frequency analysis of contrast echocardiography.

Contrast echocardiography has the potential for measuring cardiac output and regional blood flow. However, accurate quantitation is limited both by the use of non-standard contrast agents and by the electronic signal distortion inherent to the echocardiographic instruments. Thus, the aim of this study is to quantify flow by combining a stable contrast agent and a modified echo equipment, able to sample the radio frequency (RF) signal from a region of interest (ROI) in the echo image. The contrast agent SHU-454 (0.8 ml) was bolus injected into an in vitro calf vein, at 23 flow rates (ranging from 376 to 3620 ml/min) but constant volume and pressure. The ROI was placed in the centre of the vein, the RF signal was processed in real time and transferred to a personal computer to generate time-intensity curves. In the absence of recirculation, contrast washout slope and mean transit time (MTT) of curves (1.11-8.52 seconds) yielded excellent correlations with flow: r = 0.93 and 0.95, respectively. To compare the accuracy of RF analysis with that of conventional image processing as to flow quantitation, conventional images were collected in the same flow model by two different scanners: a) the mechanical sector scanner used for RF analysis, and b) a conventional electronic sector scanner. These images were digitized off-line, mean videodensity inside an identical ROI was measured and time-intensity curves were built. MTT by RF was shorter than by videodensitometric analysis of the images generated by the same scanner (p < 0.001). In contrast, MTT by RF was longer than by the conventional scanner (p < 0.001). Significant differences in MTT were also found with changes in the gain setting controls of the conventional scanner. To study the stability of the contrast effect, 6 contrast injections (20 ml) were performed at a constant flow rate during recirculation: the spontaneous decay in RF signal intensity (t1/2 = 64 +/- 8 seconds) was too long to affect MTT significantly. In conclusion, the combination of a stable contrast agent and a modified echocardiographic instrument provides accurate quantitation of flow in an in vitro model; RF analysis is more accurate than conventional processing as to flow quantitation by contrast echocardiography.

Animals↗
PubMed1993

Flow quantitation by contrast echocardiography. Effects of intervening tissue and of the angle of incidence between flow and ultrasonic beam.

The combination of a standardized echographic contrast agent with the analysis of the ultrasonic radio frequency (RF) signal allowed in vitro flow quantitation in a circulation model. The purpose of this study was to investigate both the effects of biological tissues, intervening between probe and insonated structure, and the effects of the angle of incidence between flow and ultrasonic beam on RF flow quantitation. Thus, the contrast agent SHU 454 was intravenously injected (0.4 ml) as a bolus into a circulation model, at variable flow rates, while keeping the pressure and volume of the vessel constant. Injections were performed with saline interposed between probe and vessel and after the addition of the subcutaneous tissue of a pig; injections were also performed using the probe normal to the flow and with an angle of incidence of 45 degrees. Echographic data were recorded by a mechanical sector scanner, capable of sampling the RF signal from a region of interest positioned in the center of the vein. Contrast echo time-intensity curves were generated. As expected, both peak intensity and the area under the curves decreased with intervening tissue (-58 and -70% of baseline values, respectively, p < 0.001). Surprisingly, mean transit time also decreased with intervening tissue (from 1.12 +/- 0.25 seconds with saline, to 0.92 +/- 0.13 seconds with tissue, p < 0.001), thus producing a systematic overestimation of flow (21% on the average). To compensate for signal attenuation, contrast injections were repeated in the presence of tissue after increasing the electronic signal amplification (10 dB), and transit time did not significantly differ from control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Increased echodensity of transiently asynergic myocardium in humans: a novel echocardiographic sign of myocardial ischemia.

OBJECTIVES: This study was conducted to establish whether changes in myocardial texture can be observed in humans by transthoracic echocardiography during ischemic episodes of different severity and duration induced by various pathogenetic mechanisms. BACKGROUND: Increased echo-reflectivity of ischemic myocardium has been detected in experimental animals by epicardial echocardiography and by backscatter evaluation. METHODS: Transthoracic two-dimensional echocardiographic monitoring with a commercially available electronic sector scanner (2.25- or 3.5-MHz transducer) was performed during 35 episodes of transient myocardial ischemia induced by ergonovine in patients with vasospastic angina (n = 9), by dipyridamole in patients with angiographically assessed coronary artery disease (n = 11) and by balloon occlusion during coronary angioplasty (n = 15). Quantitative texture analysis of gray levels was performed off-line on digitized images during rest conditions, ischemia and the recovery phase in regions showing normal contraction at rest, obvious dyssynergy during ischemia and normal contraction in the recovery phase. In each condition, a control region with normal contraction throughout the study was also evaluated. RESULTS: Chest pain occurred in 23 of the 35 episodes; electrocardiographic (ECG) changes were present in 26 episodes, and consisted of ST segment elevation in 13, ST segment depression in 10 and pseudonormalization of a basally negative T wave in 3. The duration of ischemic episodes was 67 +/- 53 s by symptomatic criteria and 91 +/- 52 s by ECG criteria. The risk region showed an increased end-diastolic mean gray level amplitude in a.u. (arbitrary units) during ischemia (57 +/- 19) compared with rest (38 +/- 15) and recovery (38 +/- 18, p < 0.01). No significant changes were detected in the control region (rest 36 +/- 16 vs. ischemia 34 +/- 18 vs. recovery 31 +/- 13, p = NS). The percent increase in mean gray level was similar in the various types of stress employed (ergonovine, dipyridamole or angioplasty) and was not significantly correlated with either the duration of ST segment shift (r = 0.05, p = NS) or the severity of dyssynergy evaluated semiquantitatively by means of the wall motion score (r = 0.28, p = NS). In the 15 balloon occlusions performed in six patients during coronary angioplasty, the increased echoreflectivity of the risk zone was already evident during echocardiographic sampling performed after 10 +/- 4 s of occlusion (rest 35 +/- 9 vs. 53 +/- 10 a.u., p < 0.01) when no dyssynergy could be detected by quantitative wall motion analysis (percent area change by fixed center of mass reference system 31 +/- 10% at rest vs. 32 +/- 11% after 10 s of occlusion, p = NS). CONCLUSIONS: Transient short-lasting myocardial ischemia is associated with an abrupt increase in myocardial echodensity detectable by videodensitometric analysis applied to standard transthoracic echocardiographic images and is largely independent of the underlying pathogenetic mechanism (reduced blood supply or flow maldistribution with coronary stenosis). During controlled coronary occlusion, increased echodensity precedes the onset of regional dyssynergy.

Analysis of Variance↗
PubMed1993

Effects of coronary blood flow on myocardial grey level amplitude in two dimensional echocardiography: an experimental study.

OBJECTIVE: The aims were: (1) to evaluate whether differences in absolute and cyclic echocardiographic image amplitude exist in different layers (subendocardium and subepicardium) and regions (septal, anterior, lateral, inferior wall) of the canine left ventricle; (2) to assess the dependence of these variables upon local variations of coronary blood flow. METHODS: In six anaesthetised open chest dogs the circumflex coronary artery was cannulated and perfused by a roller pump with blood from their own femoral artery. Maximum coronary vasodilatation was obtained by continuous adenosine infusion. The absolute values and the transmural distribution of coronary blood flow were measured by radionuclide labelled microspheres. Echo images were obtained in short axis view by a commercially available electronic sector scanner with a 5.0 MHz transducer directly placed on the epicardial surface of the right ventricle, and digitised off-line into a matrix of 256 x 256 pixels with 25% grey level per pixel. The average grey level was calculated for each region of interest. RESULTS: In 32 different conditions, circumflex flow ranged from 0.80 to 12.89 ml.min-1.g-1 and the endocardial/epicardial ratio of flow from 0.53 to 1.73. In the circumflex region (subjected to flow changes) segmental amplitude varied from 76(SD 20) (end diastole) to 56(18) (end systole), p < 0.001. In all regions, a consistent cyclic variation was found, ranging from 9(14) to 28(16)%. For all levels of flow, subendocardial and subepicardial regions showed similar values of both absolute amplitude and cyclic variation. No significant relationship was found between transmural distribution of blood flow and either segmental amplitude (r = 0.26) or cyclic variation (r = 0.04). CONCLUSIONS: (1) a consistent cyclic grey level variation is present in all regions of the canine left ventricle, but subendocardial and subepicardial layers show similar values of both absolute amplitude and cyclic variation; (2) in the absence of severe underperfusion and echocardiographically detectable dyssynergy, absolute amplitude and cyclic variation are totally unrelated to changes in coronary blood flow.

Animals↗
PubMed1993

Efficacy of isosorbide-5-mononitrate versus nifedipine in preventing spontaneous and ergonovine-induced myocardial ischaemia. A double-blind, placebo-controlled study.

This study was designed to assess the efficacy of oral nifedipine as compared to oral isosorbide-5-mononitrate in the prevention of spontaneous and induced vasospastic myocardial ischaemia. Twenty-one patients admitted to the Coronary Care Unit as a result of angina at rest underwent both Holter monitoring and an echo-ergonovine test during placebo and following either isosorbide-5-mononitrate or nifedipine according to a double-blind randomized trial. Both drugs caused a statistically significant reduction in spontaneous (87% and 95%, respectively) and induced ischaemic attacks (66% and 75%, respectively). No significant difference was found between the two drugs.

Administration, Oral↗
PubMed1993

Myocardial washout of sonicated iopamidol does not reflect the transmural distribution of coronary blood flow.

It has been shown in previous studies that myocardial contrast echocardiography provides quantitative information on coronary blood flow. However, the ability of contrast echo to assess the transmural (endo/epicardial) distribution of blood flow is still debated. To test this hypothesis, the left circumflex coronary arteries of six anaesthetized open-chested dogs were cannulated and perfused with blood from the femoral artery. At different rates of coronary blood flow, during adenosine-induced coronary vasodilation, sonicated iopamidol and radionuclide labelled microspheres were injected into the coronary cannula, immediately proximal to a mixing chamber. Two-D echo images were digitized and myocardial time-intensity curves were obtained for the endocardial, mid- and epicardial layers. A good correlation existed between contrast washout of the entire ventricular wall and coronary flow (r = 0.85). However, the washout rate from the endo-, mid- and epicardial layers showed weak correlations with corresponding regional blood flows measured by microspheres (r = 0.56, 0.71 and 0.58, respectively). No significant relationship was found between the endo/epicardial washout ratio and the corresponding flow ratio by microspheres. Thus, measurement of the transmural distribution of coronary blood flow by myocardial contrast echocardiography remains an elusive goal.

Animals↗